PSI - Issue 14

Anigani Sudarshan Reddy et al. / Procedia Structural Integrity 14 (2019) 449–466 Author name / Structural Integrity Procedia 00 (2018) 000–000

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Figure 10 (a-c) represents the optical micrographs of hybrid (DMLS CoCrMo on FSX414) after post weld heat treatment at 1150°C for 4 hours in vacuum. The microstructure of DMLS CoCrMo showed equiaxed grains with average grain size of 40 µm as represented in the Figure 10 (a). Figure 10 (b) represents the microstructure in the joint region indicating a sound weld between the DMLS CoCrMo and cast FSX414. Figure 10 (c) represents the microstructure of FSX414 with secondary dendrite arm spacing of 70 µm. The legends shows %porosity and grain size.

Secondary Dendrite Arm spacing = 70µm % Porosity = 0.6

Grain Size = 40 µm % Porosity = 0.05

% Porosity = 0.0038

a

b

c

100 µm

100 µm

100 µm

Fig. 10. Representative optical micrographs of hybrid of DMLS (CoCrMo on FSX-414) sample after heat treatment (a) CoCrMo (b) Welded region (c) FSX-414

Figure 11 shows the comparison of microhardness of hybrid of DMLS (CoCrMo on FSX414) at the DMLS CoCrMo, interface and Cast FSX414 regions. The hardness in the DMLS CoCrMo region is 355 HV which is same as the hardness observed in the monolithic DMLS CoCrMo after heat treatment. The substrate cast FSX414 measures around 266 HV. The hardness of the joint region is 287 HV, since this is mixed with Nozzalloy filler material.

100 150 200 250 300 350 400

0 50

Microhardness (HV)

DMLS CoCrMo Joint region

FSX414

Fig. 11. Microhardness of Hybrid DMLS (CoCrMo welded on to FSX-414) after post weld heat treatment

3.3. Tensile properties of monolithic DMLS Alloys Figure 12 (a-e) shows the representative load vs displacement curves using the small scale test specimens for all the alloys in both the as printed and heat treated condition. Table 6 is a comparison of the small scale vs the regular test specimen mechanical properties, for all the monolithic DMLS alloys. It can be seen that all the tensile properties of the small scale specimens are in close conformance with respect to the regular ASTM test results. The failure in